I cannot get this to happen here; there were similar issue with dark rendering reported by ATI users; can other people try to load dscharrer's save and report whether it happens for them as well as their system information?

I get this issue too on an HD 7770.

System Information
https://gist.github.com/Terin/ebc27bc5c56a0946c52e

A few more observations from around the same area:
It seems the skybox is not affected:

vs.

Also, there seems to be one position where only a section of the floor gets dark:

vs.

Let me know if there is anything else I can do to help track this down (or at least confidently blame it on the spectacular fglrx).

Hmm. Does it jump instantly to a higher/lower light level or fade gradually? And if the latter, if you jerk your crosshair quickly from point A to point B does the fading occur after you moved? Because if yes and yes, I'd guess it's something wrong with the HDR.

It instantly flickers between the lighting states. Sometimes without moving the camera.

It jumps instantly. Also, these maps don't seem to have HDR.

It does seem to have something to do with shadows though as it doesn't happen when setting the shadow detail to "low".

Not sure if this helps, but it also happens with mat_fullbright 1:

Also affects Episode Two. Right from the start:

I didn't encounter the issue after you get underground. In fact the whole of This Vortal Coil and Freeman Pontifex worked perfectly (except for #808, but I just turned off color correction for that). To make up for it, the bug reappeared twice as bad in Riding Shotgun: Here a) most view angles are dark, only a few are normal lit and b) reducing shadow quality to low doesn't help.

In fact, it still happens if I change all video settings to their lowest value:

Ok, poking some more cvars, I found that r_3dsky 0 "fixes" it in all cases.

Of course this means no more citadel and superportal, but at least it makes Riding Shotgun playable for now.

While this does seem to be caused by the 3d sky, not all maps with a 3d sky have this problem. For example, the last map in Episode Two (ep2_outland_12a) is lit correctly, even with r_3dsky 1 - but it clearly has a Superportal that disappears with r_3dsky 0.

For reference, this bug also happens in the Linux port of Dear Esther.

Just got this in Left 4 Dead 2 Beta at the end of Crash Course (map c9m2_lots), now with Catalyst 13.6 beta drivers:


There is no r_3dsky cvar in l4d2 though, so I couldn't check if that works there too (r_3dskyonly didn't make a difference).

Note that normally everything is too bright / washed out because of #423.

I have the same problem with Portal and to me it looks like it is related to the fact that there is a direct light source in the frame or not.
E.g it happens when I cross through a Portal for a fraction of second (when I'm just in it and it gets normal when getting out). Also, it happens when defeating GLaDOS: when looking right in the light portal on top of the room, lightning is ok; when looking down in the room, it gets darker when the light portal leaves the frame.
After the ending, when the camera runs through the conduits to the cake, it's really darker than it should be also.

Using an ATI RadeonHD 7770.

@terzag The Portal issue is tracked in #378, but yeah, they could be related.

I can no longer reproduce this with the 13.15 beta driver (aka OpenGL 4.3 beta) in HL, Ep2 and L4D2 - should this issue be closed now or when the fix is available in a stable driver version?

I think let's call it closed; great news.